By the beginning of next year, the children's meal boxes will come with a serving of strawberry yogurt and a smaller, 31-gram serving of fries that contains 100 calories.
The changes come as the fast food industry faces criticism from health officials and others, who blame the chains for childhood obesity and other health-related problems.
Louis Payette, a spokesman for McDonald's Canada, said the initiative will be tested in the fall and rolled out at the end of the year.
"It's all part of our menu evolution, which is an ongoing process," said Payette. "We're continuing to listen to our customers and trying to meet their needs. People are asking us for more variety, more choice, and we're glad to provide it to them."
McDonald's Corp. in the U.S. also announced changes to its Happy Meal on Tuesday. It plans to include a half-order of apples and a half-order of fries, with all fries or all apples available on request.
Customers can already choose between apples and fries, but only about 11 per cent of U.S. customers were ordering apples, the restaurant said.
Michelle Obama applauded the restaurant for taking a positive step toward solving childhood obesity.
But critics wasted no time complaining that the U.S. changes don't go far enough.
Kelle Louaillier, executive director of a group called Corporate Accountability International, said McDonald's is just trying to get ahead of impending regulations that will restrict the marketing of junk food to children and require restaurants to post nutrition information on menus, among other changes.
"McDonald's is taking steps in the right direction, but we should be careful in heaping praise on corporations for simply reducing the scope of the problem they continue to create," said Louaillier.
McDonald's says the new directives are "absolutely not" related to impending U.S. regulations that will force the industry to curb the marketing of junk food to children and post nutrition information on menus.
Rather, the changes are a response to what customers were asking for, said Cindy Goody, McDonald's senior director of nutrition.
"We've been in the nutrition game for over 30 years in providing nutrition information to our customers," Goody said. "Now what we're doing is we're adding more food groups and ... creating nutritional awareness."
McDonald's in the U.S. is also launching a nutrition-focused mobile phone app and pledging to reduce sugars, saturated fats, sodium and calories in its menu items by 2020.
By 2015, it will reduce sodium by 15 per cent.
But the fast food giant did not provide details on how it will do so, saying only that it will use "varied portion sizes, reformulations and innovations."
The nutrition talk also has helped McDonald's grab business from other fast-food restaurants, even as the recession forced people to cut back on eating out.
McDonald's has worked to paint itself as a healthy, hip place to eat, offering wireless access in restaurants and introducing smoothies and oatmeal, moves that other fast-food companies are now trying to replicate.
Goody said the change is indicative of "incremental lifestyle modifications." Asked why McDonald's didn't eliminate fries, she said that "all foods fit when consumed in moderation."
This isn't the first time the world's largest burger chain has tried to paint itself as an emissary of nutrition. In the '80s it created a fitness program for middle schoolers featuring gymnast Mary Lou Retton. A decade ago, McDonald's used spokesclown Ronald McDonald to encourage parents to get their children immunized and to tell kids to drink milk. In 2004, McDonald's christened Ronald a "balanced, active lifestyles ambassador" and passed out pedometers to encourage exercise.